For a three-valent graph,
the intertwiner (REF ) for each node is one-dimensional, thus it must be proportional to the \(\lbrace 3j\rbrace \) -symbol. The exact relation is well-known [1]}, with the proportionality coefficient given by a holomorphic polynomial of degree \(J_n\) . Consider three outgoing links \((l_1,l_2,l_3)\)  meeting at the node \(n\) , we denote the total spin as \(J_{123}=j_1+j_2+j_3\) . Then one gets
\(\iota ^{n}_{j_1j_2j_3}(z_1,z_2,z_3)=P_{j_1j_2j_3}(z_1,z_2,z_3)\, \iota ^{n}_{j_1j_2j_3}\,,\) 
